A technology has been known in which: cameras installed in a vehicle capture and obtain images of surroundings of the vehicle; and an amount of movement of the vehicle is obtained based on changes in the images (see Japanese Patent Application Publication No. 2008-175717). Japanese Patent Application Publication No. 2008-175717 aims at obtaining the amount of movement of the vehicle accurately even if the vehicle moves slightly at slow-speed. To this end, a feature point is detected from each image; the position of the feature point is obtained; and thereby, the amount of movement of the vehicle is obtained from the direction and distance of movement (amount of movement) of the feature point.
The above-mentioned conventional technique, however, has a problem that the amount of movement of the vehicle cannot be accurately estimated if starting points for obtaining the amount of movement of the vehicle are reset while the behavior of the vehicle is unstable.